In portrait photography, what is a "catch light"?
- Is it good or bad?
- How do I produce or avoid them?
- Are some kinds better than others?
What is a catchlight?
A catchlight is is what is used to describe the highlight that can appear in a portrait subjects eyes. This is generally a desirable thing to have because it brighteness the whites of a subjects eyes, brings out their eye color and generally adds 'life' to a subject.
Here is a 100% crop from a recent photo shoot I did using all natural lighting. The catchlight (a window) can be seen clearly reflected in the subjects eye.
As a general statement, catchlights are a great thing in portraits. It's the little 'gleam' in the eye that adds a professional sparkle to a portrait. Conversely to not have a catchlight can make a subject appear a little 'flatter' and not quite as alive.
How can I create catchlights?
While a catchlight can happen quite naturally by facing a subject towards a natural light source (and thus no artificial lighting is necessary in order for a photograph to have one), it is often something that is built into the lighting scheme by a portrait photographer using artificial lighting specifically in order to highlight the eyes.
Although this is by no means the only way to accomplish a catchlight setup, one of the most common artificial catchlight setup consists of placing a snoot over a light (snooted so that the light doesn't spill over into unwanted areas of the photograph) slightly off-axis from the camera (to avoid the potential for red-eye), dialed in to be a couple of stops under the key light (so it doesn't overpower the main lighting source), and aimed at the subject's face.
Another popular method of adding a catchlight is via a ringlight. Ringlights are desirable because of the unique circular highlight that they add to a subjects eyes, which can add a sense of the unusual, or dramatic to a picture.
(Photograph by Robert Scholler - Used with permission)
When working with a ringlight it is often necessary to move everything closer to the model in order for the ringlight to have much effect, so in general ringlight portraits are suitable for close to mid-range shots... Full shots, or anything at a distance generally will not show any benefit from a ringlight, whereas to some extent it's always possible to add more 'punch' to a snooted strobe at a distance by simply dialing up the strobe's power.
Finally, it is often easier to 'catch' a catchlight if a subject is looking slightly up. This is because most people's eyelids droop (sometimes a lot) when they look down. Looking up widens the eyelids, and thus the eyes giving a more 'alert' look and giving the light more eye to reflect off of. Commonly when my camera is below a subjects natural eye line I will have them adjust where they are looking to exploit this fact. When in doubt, have subjects look up slightly when taking their picture...
Are some catchlights better than others?
Like most things in photography, catchlights defy hard and fast rules. From natural lights, to softboxes, snoots to ringlights there are a variety of methods to achieving a catchlight, and more often than not it simply boils down to what equipment you have available, the specific needs of the shoot you're working on, and/or which of the various methods suits your photographic style the best.
My friend, a catchlight is specular reflection in the eyes, usually small. The term comes from "light catching the eyes". A symbolic representation of these catchlights is extremely popular in anime/manga-style eyes, with large, white catchlights at angles that really don't have anything to do with how light actually behaves.
Like most things in photography, it's neither inherently good or bad, it's a tool that you can use as you see fit. A lot of people like them, and they are quite popular in high-energry (high contrast) portraits, ones with rim lights, kickers and such. I have a favorite photo (which I can't find) where the model's hair is softly lit while her face is cast in darkness, with just a catchlight in her eye to give it a touch of humanity. Really nice stuff.
To produce them, point a light source at your subject in a way that produces a reflection in their eyes when you look at the model through your viewfinder. Yes, it's that easy. They're the same as any specular reflection, find your angle of incidence and go crazy. To get rid of them, do the opposite: remove your light source from a position where it can reflect in the eyes of your subject.
As to their quality, small even catchlights are often considered superior to others. Umbrella catchlights are often not optimal, as they tend to be uneven and hard to remove in post processing. Ringlights create very characteristic catchlights, some people love them, others hate them - again, it's a matter of personal choice. For a classic look, position your light to create a catchlight at about 10 or 2 o'clock on the subject's eyes.
Experiment with what works best for you. There are no right or wrong answers in photography, past "this picture works" and "this picture doesn't". Have fun with it!
Jay Lance has promised more complete examples, but here's a quick one to get the idea 'til he gets a chance:
His right eye (to the left as we see it) has a distinct catch-light. His left eye does not.
Jay Lance's answer is fantastic. Can't top that. But just thought I would provide a few good examples and mention that in the Australian film industry, we use the term 'eyelight'.